The changes made after the trial runs were found to be working. Somehow the pressure shoe seal did not wear that much even though the shower pipe on the incoming side was not in operation. The shower pipe could still be used for moisturizing the felt before starting the test runs. The seal lubrication pressure variations reduced notably after the changes, as can be observed from the following results. All the other equipment functioned well.
The tests were carried out with different loads, different shoe lubrication flows, and at different machine speeds. The trial runs carried out earlier showed that there are limits with machine speeds and pressure shoe loads for the metal belt guiding to function as desired. As observed the metal belt guiding loses its functionality after machine speed exceeds 150 m/min, while the pressure shoe seal lubrication is on. This is due to the fact that the water coming out of the nip outgoing side goes between the corner guide roll and the metal belt, which causes slipping and the metal belt loses its controllability. The same phenomenon occurs when the pressure shoe load is increased over 20 bar with pressure shoe seal lubrication. Therefore the machine speed in the following tests was chosen below the limiting speed, which is approximately 150 m/min.
The plan with test runs was at first to start with full lubrication flow for the seal and gradually increase the pressure shoe load. This was to study the correlation between different loads and
full lubrication flow to the seal wear. Between the runs the condition of the seal was monitored to observe the possible wear and failure.
The first test was carried out with the following parameters:
Machine speed: 110 m/min
Pressure shoe lubrication flow: 45 lpm
Pressure shoe loading pressure, increased in the following phases: 10, 20, 30, 40 bar.
The data collected is presented in Figure 49. As can be seen, the shoe lubrication pressure (pink line) is much more stable compared to trials presented earlier due to the change of measuring point and the added pressure accumulator. The pressure variation stays within a few bar when earlier it vibrated within 20 bar. Driving output is relatively low and it reaches approximately 1.5 kW with a load of 40 bar. The shoe lubrication pressure followed the increased load on a slightly smaller scale.
Figure 49 Test 1; speed: 110 m/min, lubrication flow: 45 lpm, loading pressure: 10 -40 bar
After the test the seal was inspected visually and the following was found:
Incoming side: Minor polishing on the back side
Outgoing side: Minor polishing throughout the whole length Front side edge: Minor scratches and polishing
Back side edge: Slightly more scratches and polishing.
The second test was done with the following parameters:
Machine speed: 110 m/min
Pressure shoe lubrication flow: 50 lpm
Pressure shoe loading pressure, increased in the following phases: 10, 20, 30, 40, 50, 60, 70, 80 bar.
As can be seen from Figure 50, with the full lubrication flow of 50 lpm and 80 bar load the driving output is approximately 2 -2.3 kW.
Figure 50 Test 2; speed: 110 m/min, lubrication flow: 50 lpm, loading pressure: 10 -80 bar
After the test the seal was inspected visually and there was not that much difference compared to traces after the earlier test. It was slightly more polished on the front side edge compared to the earlier inspection.
After the tests with different loads and full lubrication flow the effect of reducing the flow with increased pressure loads was studied. The third test was carried out with the following parameters:
Machine speed: 110 m/min
Pressure shoe lubrication flow: 30 lpm
Pressure shoe loading pressure, increased in the following phases: 10, 20, 30, 40, 50, 60, 70, 80 bar.
Figure 51 shows that with reduced lubrication flow, the driving output with the 80 bar load exceeds 3 kW. The shoe lubrication pressure remains at the same levels as with the full shoe lubrication flow.
Figure 51 Test 3; speed: 110 m/min, lubrication flow: 30 lpm, loading pressure: 10 -80 bar
After the test the seal was inspected visually and there was not that much difference compared to traces after the earlier test.
In the fourth test the lubrication flow was reduced more and the test was carried out with the following parameters:
Machine speed: 110 m/min
Pressure shoe lubrication flow: 15 lpm
Pressure shoe loading pressure, increased in the following phases: 10, 20, 30, 40, 50, 60, 70, 80 bar.
Figure 52 illustrates that the driving output exceeds 3 kW already with the 40 bar load. The shoe lubrication pressure remains at the same levels as with the full shoe lubrication flow.
Figure 52 Test 4; speed: 110 m/min, lubrication flow: 15 lpm, loading pressure: 10 -80 bar
After the test the seal was inspected visually. It was slightly more polished from the back side corners from the incoming and outgoing side compared to the earlier inspection. Also, some rubber particles were found in the pressure chamber.
The next test run was carried out with a constant pressure shoe loading and decreasing the lubrication flow from 50 lpm to 10 lpm. This was to observe the correlation between diminishing the lubrication flow and a certain load to the seal wear. The fifth test was carried out with the following parameters:
Machine speed: 120 m/min
Pressure shoe lubrication flow: decreased from 50 to 10 lpm Pressure shoe loading pressure: 20 bar.
As can be seen from Figure 53, when the amount of lubrication flow descends, the driving power required increases. The change of lubrication flow does not affect noticeably the lubrication pressure.
Figure 53 Test 5; speed: 120 m/min, lubrication flow: 50 -10 lpm, loading pressure: 20 bar
After the tests the seal was taken off the shoe and inspected. As can be seen in Figure 54 the seal is in reasonable good condition.
Figure 54 Pressure shoe seal after test runs
There is some minor polishing and wearing mainly on edge area on the front side and back side, as can be seen from Figure 55; however, overall it is in good condition.
Figure 55 Press shoe seal edges after test runs Incoming side Outgoing side
BS FS
BS edge
FS edge
BS FS
Before wad tests the seal was changed so any possible wear and damage could be observed from the new seal. Wad tests were carried out with different loads. Starting with 13 bar and gradually increasing the press shoe load to 80 bar. 80 g/m² carton strips were used as wads and the samples were put in the nip in four stages, piled up as follows. The insertion time of each wad was marked up in order to locate the impacts from the great amount of data collected.
1. 2 layers* 80 g/m² =160 g/m² 2. 8 layers * 80 g/m²= 640 g/m² 3. 20 layers * 80 g/m²= 1600 g/m² 4. 40 layers * 80 g/m²= 3200 g/m²
Tests were carried out at first with the following parameters:
Machine speed: 105 m/min
Pressure shoe lubrication flow: 28 lpm Pressure shoe loading pressure: 13 bar.
Carton was fed into the nip in the stages mentioned earlier. The insertion times were as follows:
The first wad set with two layers after 10 seconds, the second set with eight layers after 48 seconds, and the third with twenty layers after 85 seconds. Figures 56, 57, and 58 illustrate the shoe loading pressure variation in the time lines from 10 to 13 seconds, from 48 to 51 seconds, and from 85 to 87 seconds.
Figure 56 Shoe loading pressure 13 bar, 160 g/m² wad in the time line from 10 to 13 seconds
Figure 57 Shoe loading pressure 13 bar, 640 g/m² wad in the time line from 48 to 51 seconds
Figure 58 Shoe loading pressure 13 bar, 1600 g/m² wad in the time line from 85 to 87 seconds The first wad of 160 g/m² did not have a significant effect on the shoe loading pressure. The loading pressure fluctuated from a little less than 12 bar to a little over 13 bar. The second wad of 640 g/m² caused an approximately 3 bar peak on the pressure loading curve. The third wad of 1600 g/m² caused an approximately 5 bar peak on the pressure loading curve.
Figures 59, 60, and 61 illustrate the shoe lubrication pressure variation in the time lines from 10 to 13 seconds, from 48 to 51 seconds, and from 85 to 87 seconds.
Figure 59 Shoe lubrication pressure; load 13 bar, 160 g/m² wad in the time line from 10 to 13 seconds
Figure 60 Shoe lubrication pressure; load 13 bar, 640 g/m² wad in the time line from 48 to 51 seconds
Figure 61 Shoe lubrication pressure; load 13 bar, 1600 g/m² wad in the time line from 85 to 87 seconds
The first wad of 160 g/m² did not have a significant effect on the shoe lubrication pressure. The lubrication pressure fluctuated between 6 and 9 bar. The second wad of 640 g/m² caused a minor drop on the pressure lubrication curve. The third wad of 1600 g/m² caused approximately a few bar drop on the pressure lubrication curve. After the test the seal was inspected visually and only some minor polishing was discovered.
The second wad test was carried out with the following parameters:
Machine speed: 105 m/min
Pressure shoe lubrication flow: 22 lpm Pressure shoe loading pressure: 38 bar.
Carton was fed into the nip in the stages mentioned earlier. The insertion times were as follows:
the first wad after 7 seconds, the second after 34 seconds, and the third after 73 seconds. Since the third wad made the largest impact, the Figure 62 illustrates the shoe loading pressure variation in the time line from 73 seconds until 75 seconds.
Figure 62 Shoe loading pressure 38 bar, 1600 g/m² wad in the time line from 73 to 75 seconds
Figure 63 illustrates the shoe lubrication pressure variation in the time line from 73 seconds until 75 seconds.
Figure 63 Shoe lubrication pressure; load 38 bar, 1600 g/m² wad in the time line from 73 to 75 seconds
The third wad of 1600 g/m² caused an approximately 5 bar peak on the pressure loading curve and approximately a few bar drop on the pressure lubrication curve. After the test the seal was inspected visually and there was some more minor polishing.
The third wad test was carried out with the following parameters:
Machine speed: 105 m/min
Pressure shoe lubrication flow: 18 lpm Pressure shoe loading pressure: 60 bar.
Carton was fed into the nip in three stages. The insertion times were as follows: the first wad after 23 seconds, the second wad after 44 seconds, and the third wad after 63 seconds. Figure 64 illustrates the shoe loading pressure variation in the time line from 44 seconds until 46 seconds.
Figure 64 Shoe loading pressure 60 bar, 1600 g/m² wad in the time line from 44 to 46 seconds Figure 65 illustrates the shoe lubrication pressure variation in the time line from 44 seconds until 46 seconds.
Figure 65 Shoe lubrication pressure; load 60 bar, 1600 g/m² wad in the time line from 44 to 46 seconds
The third wad of 1600 g/m² caused an approximately 6 bar peak on the pressure loading curve and an approximately 5 bar drop on the pressure lubrication curve. After the test the seal was inspected visually and there was again some more polishing.
The fourth wad test was carried out with the following parameters:
Machine speed: 105 m/min
Pressure shoe lubrication flow: 42 lpm Pressure shoe loading pressure: 80 bar.
Carton was fed into the nip in the stages mentioned earlier. The insertion times were as follows:
the first wad after 25 seconds, the second wad after 36 seconds, the third wad after 45 seconds, and the fourth wad after 86 seconds. Figure 66 illustrates the shoe loading pressure variation in the time line from 86 seconds until 88 seconds.
Figure 66 Shoe loading pressure 80 bar, 1600 g/m² wad in the time line from 86 to 88 seconds
Figure 67 illustrates the shoe lubrication pressure variation in the time line from 86 seconds until 88 seconds.
Figure 67 Shoe lubrication pressure; load 60 bar, 1600 g/m² wad in the time line from 44 to 46 seconds
The third wad of 1600 g/m² caused an approximately 15 bar peak on the pressure loading curve and an approximately 10 bar drop on the pressure lubrication curve. After the wad tests the seal was taken out of the shoe and inspected. As Figure 68 illustrates, there was some wear on the incoming side. Also, both edge areas on the front side and the back side were worn. The outgoing side was almost intact. Overall, the condition of the seal was relatively good.
Figure 68 Press shoe seal after wad tests Outgoing side
Incoming side
FS BS